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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'bf6f21b098f4430c4e6c9dec7886fdcd4171b0c00c4da49c07fa9c6fabf39d57' 
  AND token = 'ceFEL/EVr+3NsC5VZP5UTACrS2RiAsbnPbaSeVb/GNU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}